In recent years, short-arc high-pressure discharge lamps, in which mercury vapor pressure is for example at least 20 MPa, have been attracting attention as a light source for projection image display devices such as liquid crystal projectors. This is because such high-pressure discharge lamps provide nearly point-source light. Furthermore, due to high mercury vapor pressure during lighting, such lamps are expected to achieve high-intensity light with high color rendering.
Short-arc high-pressure discharge lamps have a structure that includes a glass arc tube and a pair of electrodes. The arc tube includes a light-emitting part, which is provided with a discharge space therein, and sealing parts connected to the light-emitting part. The electrodes are each embedded in the corresponding sealing part so that one end thereof faces the other electrode in the discharge space, while the other end is connected to a metal foil (see, for example, Patent Literature 1). Note that the high-pressure discharge lamp may simply be referred to as a “lamp”.